Focused electron flow electron tube for very high frequencies



July 22, 1958 w. VEITH ET AL 2,844,750

FOCUSED ELECTRON FLOW ELECTRON TUBE FoR VERY HIGH FREQUENCIES Filed July 18, 1955 2 Sheets-Sheet 1 (PR/0A Am) flvmfars.

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' July 22, 1958 E w. VEITH ET AL Y 2,844,750

1 FOCUSED ELECTRON FLOW ELECTRON TUBE Filed July 18. 1955 FOR VERY HIGH FREQUENCIES 2 Sheets-Sheet 2 flaws 076. M77ZW 7493614, 5

United States Patent FOCUSED ELECTRUN FLOW ELECTRON TUBE FOR VERY HIGH FREQUENCIES Werner Veith and Paul Meyerer, Munich, Germany, as-

slgnors to Siemens & Halske Aktiengesellschaft, Munich and Berlm, Germany, a corporation of Germany Application July 18, 1955, Serial No. 522,615

Claims priority, application Germany September 22, 1954 14 Claims. (Cl. 31384) This invention is concerned with focused electron flow electron tubes for very high frequencies.

Focused electron flow is used in numerous tubes for very high frequencies, particularly in tubes operating in the nature of traveling wave tubes, special means being in such cases required for guiding the concentrated electron flow along extended paths. Magnet coils traversed by current are usually employed for this purpose. It is, however, in many cases suitable to use a magnet system comprising permanent magnets.

Magnet systems having permanent magnets have been proposed for such tubes, comprising atubular interior guide provided at its ends with annular extensions connected at their outer margins with magnet rods. It is in numerous cases of tubes of this kind, for example, traveling wave tubes necessary, for the coupling of the high-frequency energy, to provide the interior guide tube with a suitable hollow conductor forming apertures corresponding to its cross-section. The disturbance of the rotation symmetry of the magnetic field, caused by such apertures may be held small if the guide tube is stepped following the apertured parts.

It has now been discovered that the above noted construction brings about a deterioration of field strength progressing in longitudinal direction of the magnet system. Theofiset configuration of the inner width in the vicinity of the transition point causes an increase of the field strength in the reduced guide tube and decrease thereof at the other end of the magnet system.

The object of the invention is to correct the progression of the magnetic field'within the cross-sectionally reduced portion of the magnetsystem and above all to avoid a decrease of the field strength toward the end of the system. In a traveling wave tube, such a decrease would bring about splitting of the electron flow and therewith an impermissible increase of the electron fiow to the delay line.

The invention is based upon recognition of the fact that identical field strength may be expected to obtain in the wide and in the narrow portions of the guide tube only when the annular extension which forms the transition between the narrow and the wide inner spaces satis fies strictly predetermined conditions. The magnetic impedance of the transition must thereby be such that the decrease of the magnetic force occurring thereat per unit of length causes the surplus lines of force of the wide part of the guide tube to enter in parallel into the wall thereof.

Based upon this reasoning, the invention provides for affecting the magnetic impedance at the place of transition, by multiple formation of the magnet system at such place and by variable magnetic parallel connection of auxiliary system parts, so as to bring about, along the narrow inner space, a substantially homogeneous or an increasing field progression. An annular disk or the like, made of soft magnetic material may thereby serve as an auxiliary system part.

.ferent outer diameter.

2,344,750 Patented July 22, 1958 v The reduction of the magnetic impedance may be effected by means of disks of different thickness or of dif- It is also possible to vary the number of the disks which may be piled up or arranged in mutually embracing relationship. Aside fromv the rough variation in steps, it is possible to effect a continuous variation alone or additionally by varying the spacing of the annular disk from the transition member of the magnet system between the narrow and the wide inner spaces.

The various objects and features of the invention will appear from the description which will be rendered below with reference to the accompanying diagrammatic drawings in which:

Fig. 1 shows the magnet system of a known travelling wave tube in schematic sectional view;

Fig. 2 indicates in the form of curves the field strength progression in the interior of the magnet system as it occurs in the known arrangement as contrasted with the progression of the magnetic field provided by the invention;

Fig. 3 shows the magnetic lines of force at the place of transition;

Fig. 4 illustrates in sectional view a travelling wave tube such as shown in Fig. 1 but comprising in accordance with the invention a disk forming the auxiliary means disposed in the magnet system;

Fig. 5 is a partial view showing an auxiliary disk mounted so that the spacing thereof from a neighboring wall member may be varied; and

Figs. 5a, 5b show respectively a plurality of disks of different thickness and different diameter, for use as the auxiliary disk means in the magnet system according to the invention.

In Fig. 1, numeral 1 indicates the inner guide tube of the magnet system, such tube being connected with an enlarged tube 3 by means of an annular wall 2. The enlargement is dimensioned so as to permit insertion of the hollow input conductor at 4 and also insertion of the tube part indicated at 5. Two annular end plates 6 and 7 serve for connection with the outer magnet system which may be formed by a tubular permanent magnet or by arnumber of individual magnet rods as indicated at 8 and 9. e 1 I The field strength progression, resulting in a structure such as shown in 1 corresponds substantially to the dot-dash curve 0 indicated in Fig. 2.

The field progression which is according to the invention desired is indicated by the full line curve a of Fig. 2. In order to obtain such field progression or characteristic, it is necessary, as shown in Fig. 3, to make the magnetic impedance of the transition such that the decrease of the magnetic force per unit of length, that is, the magnetic excitation, causes the surplus lines of force of the enlarged part of the guide tube to enter in parallelism into the transverse wall thereof. The lines of force are symbolized by the arrows 10. The remaining numerals indicate parts similarly referenced in Fig. 1.

Inasmuch as variations of the permeability of the magnetic material sufiice within the tolerance thereof to vary the magnetic impedance so as to provide for a progression of the field strength as indicated by the curves b and c of Fig. 2, it will be necessary to vary the impedance of the transition after magnetizing the magnet. The impedance of the transition is for this purpose intentionally made too high. The result is a progression which is substantially in accordance with curve b of Fig. 2. A second or several further impedance magnitudes are connected in parallel with this magnetic impedance, which is accomplished by disposing an annular disk or the like or several such disks, made of soft magnetic material,

directly in front of the annular wall 2 or in a predetermined spacing relative thereto.

An example of such an arrangement appears in Fig. 4, parts corresponding to those shown in Figs. 1 and 3 being again indicated by like reference numerals. The auxiliary or added system part is in the form of an annular disk 11 with predetermined thickness and outer diameter. The thickness and the outer diameter of the disk may be different in accordance with the requirements for the stepwise alteration of the magnetic impedance.

The spacing of the disk from the transition wall 2 may be varied by known and suitable adjustment means so as to provide for continuous variation of the magnetic impedance. Fig. shows as an example how the disk 11 (also shown in Fig. 4) may be adjustably mounted on the transverse transition wall 2 by means of screws 12, made of insulating material, permitting adjustment of the spacing from the wall 2.

A plurality of disks such as 11 may be provided in a pile or disposed concentrically one within the other so as to provide for desired stepwise variation of the thickness and outer diameter, respectively. The disks may be of difierent thickness or of different diameter, if desired. Thus, disks such as 11a, 11b, of different thickness, shown in Fig. 5a or disks 11c, 11d, of difierent diameter, as shown in Fig. 5b, may take the place of disk 11 shown in Figs. 4 and 5. The disks may of course be provided in desired combinations, for example, exhibiting identical or different thickness as well as diflerent diameter.

Changes may be made within the scope and spirit of the appended claims.

We claim:

1. A focused electron flow electron tube for very high frequencies comprising a magnet system including permanent magnet means, tubular means connected with said permanent magnet means forming an inner longitudinally extending chamber for guiding the electron flow along an extended path formed thereby, said tubular means comprising an enlarged portion disposed at least at one end of said magnet system and a narrower portion axially extending therefrom, a plurality of parts forming the transition from said narrower to said enlarged portion, said parts being arranged for variable magnetic connection to afiect the magnetic impedance at said transition so as to produce a predetermined field progression within said narrower portion of said chamber. a

2. A structure and cooperation of parts according to' 3. A structure and cooperation of parts according to claim 1, wherein a substantially homogeneous field progression is produced within said narrower portion of said chamber.

4. A structure and cooperation of parts according to claim 1, wherein a rising field is produced within said narrower portion of said chamber.

5. A structure and cooperation of parts according to claim 1, comprising wall means extending between said enlarged and said narrower portions, and auxiliary means cooperating magnetically with said wall means.

6. A structure and cooperation of parts according to claim 5, comprising at least one magnetic disklike member of soft material constituting said auxiliary means.

7. A structure and cooperation of parts according to claim 5, comprising a plurality of disklike members constituting said auxiliary means.

'8. A structure and cooperation of parts according to claim 5, comprising a plurality of disklike members of different thickness constituting said auxiliary means.

9. A structure and cooperation of parts according to claim 5, comprising 'a plurality of disklike members of different outer diameter constituting said auxiliary means.

10. A structure and cooperation of parts according to claim '5, comprising means for varying the spacing of said auxiliary'means relative to said wall means.

11. A structure and cooperation of parts according to claim 6, comprising means for varying the spacing of said disklike member relative to said wall means.

12. 'A structure and cooperation of parts according 'to claim 7, comprising means for varying thespacing of said disklike members relative to said wall means.

13; A structure and cooperation of parts according to claim 8, comprising means for varying the spacing of said disklike members relative to said wall means.

14. A structure and cooper'ation'of parts according to claim 9, comprisin means for varying the spacing of said disklike members relative to said 'wall means.

2,149,101 Ploke Feb. 28, 1939 2,200,039 Nicoll May 7, 1940 2,219,193 Mynall Oct. 22, 1940 2,305,761 Borries et a1 Dec. 22, 1942 2,403,529 Hillier et al. July 9, 1946 2,619,607 Steers Nov. 25, 1952 

